The two broad objectives of the current proposal are (a) to understand the potential relationship between speech breathing and articulation in persons with motor speech disorders, and (b) to develop a statistical model of articulatory variability in persons with motor speech disorders, and to use this model to explain the basis of speech motor control deficits in this population. More specifically, the aims of the proposed studies are (a) to understand how modifications in the starting lung volume for speech affect acoustical and perceptual measures of articulatory behavior, (b)to determine if persons with motor speech disorders are able to learn consistent modification of their starting lung volumes for speech, and (c) to study the statistical relationships between spectral and temporal properties of formant transitions produced by persons with motor speech disorders. The experimental plan to address these aims includes natural observation of the covariation between lung volume variables and the acoustical/perceptual measures mentioned above, single-case design methods to evaluate patients' ability to learn the lung volume modifications, and a paradigm in which speaking rate is intentionally varied for the purpose of inducing variability in articulatory processes. When the specific aims identified above are met, there should be a much better understanding of the factors contributing to communication deficits in persons with neurological disease, and hence a better notion of how best to treat the deficit.